This application claims priority from and incorporates by reference Indian Patent Application No. 846/Mum/2001, filed Sep. 3, 2001.
Cashew nut shell liquid (CNSL) occurs as a reddish brown viscous liquid in the soft honeycomb structure of the shell of cashewnut, a plantation product obtained from the cashew tree, Anacardium Occidentale L. Native to Brazil, the tree grows in the coastal areas of Asia and Africa. Cashewnut attached to cashew apple is grey colored, kidney shaped and 2.5-4 cm long. The shell is about 0.3 cm thick, having a soft leathery outer skin and a thin hard inner skin. Between these skins is the honeycomb structure containing the phenolic material popularly called CNSL. Inside the shell is the kernel wrapped in a thin brown skin, known as the testa.
The nut thus consists of the kernel (20-25%), the shell liquid (20-25%) and the testa (2%), the rest being the shell. CNSL, extracted with low boiling petroleum ether, contains about 90% anacardic acid and about 10% cardol. CNSL, on distillation, gives the pale yellow phenolic derivatives, which are a mixture of biodegradable unsaturated m-alkylphenols, including cardanol. Catalytic hydrogenation of these phenols gives a white waxy material, predominantly rich in tetrahydroanacardol.
CNSL and its derivatives have been known for producing high temperature phenolic resins and friction elements, as exemplified in U.S. Pat. Nos. 4,395,498 and 5,218,038. Friction lining production from CNSL is also reported in U.S. Pat. No. 5,433,774. Likewise, it is also known to form different types of friction materials, mainly for use in brake lining system of automobiles and coating resins from CNSL. However, the first application of CNSL in making lubricating oil additives was disclosed by us in U.S. Pat. Nos. 5,916,850 and 5,910,468.
The general term to describe the moisture corrosion is rusting. Rusting is caused by electrochemical attack of oxygen through water on the ferrous metal surfaces of the gear. The rusting is greatly aggravated by the presence of sulphur and phosphorus compounds (EP and AW additives) and their thermal, oxidation or hydrolytic decomposition by-products. A good automotive or industrial gear oil should have ample rust preventive characteristics built-in to combat all eventualities.
Rust is the common oxidative corrosion on iron and its alloys and is the result of an electrochemical reaction. A great deal of research to develop means of controlling or eliminating rust has been conducted. Strategies to control the rust include eliminating oxygen or preventing the electrolyte and oxygen from interacting at the metal surface, the conditions not practically possible, or by the use of polar compounds known as rust inhibitors.
Rust inhibitors are generally surface active agents consisting of polar compounds. The structure of these polar compounds consists of a xe2x80x9cheadxe2x80x9d which has a strong affinity for the metal surface and a hydrocarbon xe2x80x9ctailxe2x80x9d which orients itself away from the surface. These molecules form a tightly adsorbed monolayer, which prevents moisture and oxygen from reaching the metal surface. Common Chemistries of the polar head of these molecules includexe2x80x94Carboxylic acids, their esters, sulphonates, imidazolines, amines etc., performance of each class of the rust inhibitor depends upon:
Type of the other additives present in the system
Service conditions
Metallurgy type to be protected
An exhaustive literature review was conducted to examine the types of Chemistries in use for selection of the rust inhibitors for use in blending modern grades of gear lubricants. There was hardly any published literature correlating the performance of a RI with its Chemistry. However, there are a sizable number of patent references for development of rust inhibiting additives for gear oil applications. These include U.S. Pat. No. 6,180,575 (Jan, 2001. Mobil) for mixture of substituted benzotriazole and amine phosphates, U.S. Pat. No. 6,165,952 (Dec, 2000. Kings Industries) for mixture of condensed polyacids and amines, U.S. Pat. No. 5,358,650 (Oct, 1994. Ethyl) mixtures of aminosuccinic esters and dimer acids, U.S. Pat. No. 4,247,414 (Jan, 1981, Nippon), mixtures of alkylphenoxy ethyleneglycol and phosphate esters. Other patents which describe corrosion inhibiting compositions of gear oils include U.S. Pat. No. 5,055,230 (Oct, 1991, Ciba-Geigy), U.S. Pat. No. 4,493,776 (Jan, 1985, Shell) U.S. Pat. No. 4,427,565 (Jan, 1984, Standard Oil), U.S. Pat. No. 5,487,846 (Jan, 1996, Union Chemicals) and U.S. Pat. No. 3,909,215 (Sept, 1975, Chevron).
Literature review revealed that a large number of additives with different chemistries have been developed and used in gear oil compositions. Also, it has become increasingly evident that for passing CRC L-33 corrosion test, a combination of additives had to be used. This makes sense as L-33 rig contains parts having different metallurgies, i.e., cover plates, pinion and gears and the effective RI should be able to protect all these parts which count in the corrosion rating.
The present invention relates to lubricant compositions and more particularly, to lubricant compositions comprising oils of lubricating viscosity or greases thereof containing a minor rust inhibiting additive of alkyl phenoxy carboxylic acids and their esters or amides derived from cashew nut shell liquid.
Recently, our U.S. Pat. No. 5,916,850 described development of multifunctional additives from cashew nut shell liquid or from saturated alkylphenols derived from cashew nut shell liquid. The patent relates to a process for preparing di(alkylaryl)phosphorodithioate. The products of this invention were found to have better antifriction, extreme pressure and antiwear properties. In another U.S. Pat. No. 5,910,468, cashew nut shell liquid has been exploited for developing overbased calcium phenate detergents as additives for lubricant formulations.
The object of the present invention is to provide for a rust inhibiting alkyl phenoxy acetic acid/ester based lubricant/fuel additive, derived from CNSL, a renewable and biodegradable product from vegetable sources and often available at very low price, which would amount to substantial overall reduction in the cost of quality, energy efficient lubricant/fuel formulations.
Another object of the present invention is to provide for a lubricant composition and more particularly, to lubricant compositions comprising oils of lubricating viscosity or greases thereof containing a minor rust inhibiting additive derived from alkyl phenoxy acetic acid/ester derived from cashew nut shell liquid.
To achieve the said objects, the present invention provides a process for the preparation of alkyl phenoxy carboxylic acid/ester for use as an additive in a lubricant composition by reacting said cashew nut shell liquid with halo carboxylic acid or ethyl chloroacetate to obtain corresponding unpolymerized cashew nut shell liquid alkyl phenoxy carboxylic acid/ester, the reaction being carried out at a temperature ranging from 20 to 140xc2x0 C. Alternatively, rust inhibitor can be synthesized by first hydrogenating distilled technical cashew nut shell liquid (CNSL) with a catalyst as herein described to fully hydrogenate the olefinic chain and reacting said cashew nut shell liquid with halo carboxylic acid or ethyl chloroacetate to obtain corresponding unpolymerized cashew nut shell liquid alkyl phenoxy carboxylic acid/ester.
The Carboxylic acids required to produce the additive compositions of the present invention have 1 to 3 carboxyl based groups, and contain a halogen substituted hydrocarbon based aliphatic or alicyclic group that is, a group having a halogen atom attached directly to an aliphatic or alicyclic carbon atom, i.e., a carbon atom that is part of an aliphatic or alicyclic based group. The halogen atom in these carboxylic acid reagents is preferably chlorine or bromine. More preferably, the chlorine or bromine atom is bonded to a carbon alpha to at least one of the carboxyl based groups present.
Carboxyl based groups include free carboxylic acid groups as well as carboxylic anhydride groups, carboxylate salts of any of the metals, carboxylic acid ester groups of mono and polyhydric alcohols and carboxylic acid nitrogen containing groups such as carboxamide and ammonium carboxylate groups of the amino compounds.
Among the particularly preferred carboxylic acid reagents used to produce the compositions of this invention are alpha halo carboxylic acid reagents having 2 to 20 carbon atoms and being aliphatic or alicyclic based. Examples of carboxylic acid reagents are chloroacetic acid, ethyl chloroacetate, chloro succinic anhydride, chloro glutaric acid, sodium chloro acetate, methyl chloro stearate. Other appropriate halo carboxylic acid reagents within the scope defined above will readily occur to those skilled in the art.
The present invention further includes a lubricant composition comprising a major proportion of a material selected from the group consisting of an oil of lubricating viscosity and a grease and remainder an additive comprising cashew nut shell liquid alkyl phenoxy carboxylic acid/ester
The additive is present in an amount ranging from about 0.01 to about 5 wt %, preferably 0.03 to 3 wt %.
The oil of lubricating viscosity is selected from the group consisting of a mineral oil, a synthetic oil, and mixtures thereof.
The said synthetic oils includes polypropylene glycol, trimethylol propane esters, neopentyl and pentaerythritol esters, polyethylene glycol, di(2-ethylhexyl) adipate, fluorocarbons, siloxanes, phenoxy phenyl ethers and polyalphaolefins.
The lubricant composition may include other additives such as polyalkyl succinimide and polyalkenyl ester dispersants, metallic (calcium or magnesium) sulfonates or phenates, metallic phosphorodithioates and polymeric viscosity index improvers, etc.
The said material is a grease selected from the group consisting of a lithium grease, a calcium grease, a sodium grease, a clay, and a titanium grease.
This invention is more particularly directed to lubricant compositions containing minor additive concentrations of alkyl phenoxy carboxylic acid derivatives, derived from hydrogenated distilled cashew nut shell liquid, and a major amount of oil of proper lubricating viscosity, which exhibit excellent rust inhibiting properties. Concentrations as little as 0.03% in fully formulated synthetic and mineral oil based formulations control the rusting tendency due to other additives.
Generally speaking, the process of manufacturing the additives in accordance with this invention may be carried out as follows:
Specifically, cashew nut shell liquid is distilled at reduced pressure to yield a mixture of biodegradable olefinic phenols. The components of CNSL contain a phenolic hydroxyl group and an C15H31-n unsaturated side chain, where n=0,2,4 or 6. Such a mixture is used as such or converted to their saturated C15 phenol derivatives by catalytic reduction in the presence of a palladium or platinum or nickel hydrogenation catalyst. The alkyl phenol is treated with halo carboxylic acid derivative in alkaline media in the presence of a solvent. After the completion of the reaction, the solvent is removed and product extracted with another organic solvent to yield the desired CNSL phenoxy carboxylic acid derivatives.
The lubricants contemplated for use herein include both mineral and synthetic hydrocarbon oils of lubricating viscosity, mixtures of mineral and synthetic oils and greases prepared therefrom.
The following examples illustrate the invention, but without intending to imply any limitation thereon.